The present inventive concept relates to semiconductor memory devices and incorporating memory systems.
Semiconductor memory devices may be generally classified as volatile and nonvolatile in their operative nature. Volatile semiconductor memory devices lose stored data in the absence of applied power. Nonvolatile memory devices retain stored data when power is interrupted.
Volatile memory devices include static random access memories (SRAM), dynamic random access memories (DRAM), and synchronous dynamic random access memories (SDRAM). Nonvolatile memory devices include read only memories (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically EPROM (EEPROM), flash memories, phase-changeable random access memories (PRAM), magnetic random access memories (MRAM), and ferroelectric random access memories (FRAM). Flash memories are further classified into two types, i.e., NOR-type flash memories and NAND-type flash memories.